최정우 교수

This article addresses the way in which we can generate an "acoustically bright zone" in a space. The bright zone is defined as the volume where we can have higher acoustic energy than in other space. A method is proposed to generate the bright zone by controlling multiple monopole sources. Two kinds of cost functions involved with acoustic brightness are defined. One is the ratio of the brightness of a zone to the input power, and the other expresses the "contrast" between the bright zone and t

A graphene thermoacoustic loudspeaker with a thin polymer mesh is fabricated using screen-printing. An experiment with substrates of various free-standing areas shows that a higher sound pressure level can be achieved as compared to previously reported graphene thermoacoustic loudspeakers. Moreover, a modified equation to predict the sound pressure level of the thermoacoustic loudspeaker with a thin and patterned substrate is proposed and verified by experimental results.

We built a thermoacoustic loudspeaker employing N-doped three-dimensional reduced graphene oxide aerogel (N-rGOA) based on a simple template-free fabrication method. A two-step fabrication process, which includes freeze-drying and reduction/doping, was used to realize a three-dimensional, freestanding, and porous graphene-based loudspeaker, whose macroscopic structure can be easily modulated. The simplified fabrication process also allows the control of structural properties of the N-rGOAs, incl

This study aimed to identify the clinicopathological features of bladder cancer patients with high CD74 expression, as milatuzumab humanized anti-CD74 antibody is being evaluated in clinical trials for hematological malignancies. Expression of CD74 was examined in 342 urothelial carcinomas of the bladder, and two urothelial carcinoma cell lines by immunohistochemistry and western blotting, respectively. CD74 was overexpressed in 192 (56.1%) of the 342 cancer tissues, although it was not expresse

In this paper, the authors propose a method of enhancing sound in a selected region by controlling multiple sources. The physical variables of enhancing sound have not been well defined, but we may consider basic acoustic variables such as acoustic potential energy, sound power or intensity. A method of maximizing sound potential energy was found to be very straightforward [J.-W. Choi and Y.-H. Kim, J. Acoust. Soc. Am. 111, 1695 (2002)]. In this paper, the authors attempt to control the sound po

The eigenbeam estimation of signal parameters via the rotational invariance technique (EB-ESPRIT) is a well-known subspace-based beamforming algorithm for a spherical microphone array. EB-ESPRIT uses a recurrence relation to directly estimate directional parameters expressing directions-of-arrival (DOAs) of sound sources without an exhaustive grid-search. In the conventional EB-ESPRIT, the directional parameter along the elevational direction is given by a tangent function, which inevitably prod

A method for reproducing a desired sound field by using an array of loudspeakers is proposed. A virtual sound source that generates the desired sound field can be located at either the outside or inside a loudspeaker array; however, a complete reproduction of the virtual source located inside the array is physically not possible because the sound field from the internal virtual source should satisfy the inhomogeneous wave equation. When time reversal is used for removing such inhomogeneity, conv

A 3D sound source localization (SSL) technique for multiple spherical arrays is proposed. Spherical arrays have been popularly used for direction of arrival (DoA) estimation, which serves as important prior knowledge for source separation, dereverberation, and binaural rendering for VR applications. In this work, a parametric 3D SSL technique is proposed that can detect multiple sources using multiple spherical array recordings. From the enriched information by using multiple arrays, we show tha

BACKGROUND: Algorithms for primary human papillomavirus (HPV) screening, primary HPV screening plus cytology cotesting, and cytology alone were evaluated previously in large cohort trials for cervical cancer detection, although the quality of cytology in those studies was controversial. To investigate whether these 3 algorithms would be applicable in routine practice at a tertiary care hospital, the authors compared their clinical performance. In addition, the prevalence of HPV genotypes was det

We derived an integral equation for reproducing the sound field of a virtual source inside an array of loudspeakers with reduced radiation to the outside. Reproduction of a sound field over a finite interior region inevitably generates sound waves that propagate outside the region. This undesirable radiation is reflected from walls and can induce artifacts in the interior region. In principle, the Kirchhoff-Helmholtz (KH) integral can be used to reproduce the interior sound field from an exterio

Multichannel filters to synthesize a personal sound zone are often designed in frequency domain. The frequency domain design assumes a circular convolution between impulse responses of loudspeakers and filter coefficients, and hence, the actual sound pressure field produced by the linear convolution with the impulse responses differs from the sound field predicted at the design stage. The circular convolution issue can be resolved by the time domain filter coefficient design, but in this case th

PURPOSES : This study drew factors affecting motorcycle accidents in Seoul by severity using an ordered probit model and aimed to analyze and verify the drawn influence factors. METHODS : As the severity of the accidents could be classified into three types (fatal injury, serious injury and minor injury), this study drew the factors affecting accidents by a comparative analysis employing an ordered probit model, removed the variables that would not secure significance sequentially to construct a

Abstract The sound pressure generated by thermo‐acoustic (TA) loudspeakers is proportional to the frequency of the sound. This characteristic yields a low sound pressure level (SPL) in the low‐frequency region, hindering the practical application of TA loudspeakers. The limitation of low SPL is approached by using a resonating structure, in which a TA sound generator, such as multiwalled carbon nanotube sheet, is enclosed within a cavity covered by a vibrating plate. However, the cavity‐plate re